1. Field of the Invention
The invention relates to a solenoid valve, and more particularly to a self-latch solenoid valve using a mechanism without a permanent magnet.
2. Description of the Related Art
A conventional self-latch solenoid valve switches a stretching position and a shrinking position via electrification to a coil. After cutting off the power supply, a rod holds the same position as that before cutting off the power supply. After cutting off the power supply, the conventional self-latch solenoid valve attracts the rod via magnetic force of a magnet for saving power and the rod is fixed at the shrinking position so that a normal open function is provided by the solenoid valve.
FIG. 1A is a schematic view of a conventional self-latch solenoid valve. FIG. 1B is a schematic view of the conventional self-latch solenoid valve in FIG. 1A that a part of its structure is removed. As shown in FIGS. 1A and 1B, the solenoid valve 5 includes at least a permanent magnet 51, a rod 52, a coil 53, and a spring 54.
The rod 52 of the solenoid valve 5 shown in FIG. 1B is disposed at a shrinking position F. When applying a current to the solenoid valve 5, the coil 53 generates excitation phenomenon to provide a magnetic attraction to attract the rod 52. The rod 52 moves from a stretching position E to the shrinking position F. When the rod 52 moves to the shrinking position F, the permanent magnet 51 is attracted to fix the rod 52. At this time, a power source is closed and the permanent magnet 51 continues to attract and fix the rod 52. Thus, the normal open function is provided for the solenoid valve 5.
To apply a reverse current (contrary to the direction of the current on the above-mentioned paragraph) to the coil 53, a reverse magnetic field is generated to neutralize the magnetic force of the permanent magnet 51 so that the spring 54 pushes the rod 52 to the stretching position E. At this time, the power source is closed and a normal close function is provided for the solenoid valve 5.
However, when using the solenoid valve 5, a driving circuit must include a positive and a negative phase bridge circuit to control the solenoid valve 5 and reduce energy resource waste for saving power. The solenoid valve 5 generally includes an attached mechanism 55 for fixing the permanent magnet 51. The above-mentioned design substantially increases manufacturing costs.
FIG. 2A is a schematic view of another conventional self-latch solenoid valve. FIG. 2B is a schematic view of the other self-latch solenoid valve in FIG. 2A that a part of its structure is removed. A solenoid valve 6 includes at least a permanent magnet 61, a rod 62, a first coil 631, a second coil 632, a spring 64 and an attached mechanism 65 for fixing the permanent magnet 61.
Referring to FIGS. 2A and 2B, the rod 62 of the solenoid valve 6 is disposed at the stretching position E. Referring to FIG. 2B, when applying a current to the first coil 631, the first coil 631 generates excitation phenomenon to provide a magnetic attraction to attract the rod 62. The rod 62 moves from the stretching position E to the shrinking position F. When the rod 62 moves to the shrinking position F, the permanent magnet 61 is attracted to fix the rod 62. At this time, a power source is closed and the permanent magnet 61 continues to attract and fix the rod 62. Thus, a normal close function is provided for the solenoid valve 6.
When applying a current to the second coil 632, the second coil 632 generates excitation phenomenon to provide a magnetic attraction to attract the rod 62 in a reverse direction. The rod 62 moves from the shrinking position F to the stretching position E. When the rod 62 moves to the stretching position E, the rod 62 is divorced from the attraction of the permanent magnet 61. At this time, the spring 64 provides fixation for the rod 62 to make sure the rod 62 to hold at the stretching position E. Then, a power source is closed and the normal close function is provided for the solenoid valve 6.
The solenoid valve 6 is equipped with a digital switching on a circuit for controlling and switching the first and second coils 631, 632 of the solenoid valve 6 so that the energy resource waste can be reduced and the power can be saved. The solenoid valve 6 generally has the attached mechanism 65 for fixing the permanent magnet 61 and includes the first and second coils 631, 632. The above-mentioned design not only increases the number of elements but also manufacturing cost and complexity.